Slab laser design and usage are well known in the art. One such slab laser device is illustrated in U.S. Pat. No. 4,559,627, issued to Myung K. Chun on Dec. 17, 1985, entitled FACE-PUMPED RECTANGULAR SLAB LASER APPARATUS HAVING AN IMPROVED OPTICAL RESONATOR. Another such slab laser device is shown in U.S. Pat. No. 4,214,216, issued to William B. Jones, Jr., on Jul. 22, 1980, entitled FACE-PUMPED LASER WITH DIFFRACTION-LIMITED OUTPUT BEAM.
Despite the flurry of activity in this field, the current slab laser systems have not attained a performance level that is sufficient to produce a commercially viable apparatus.
A typical slab laser device is characterized as a laser medium having a configuration in the shape of a trapezoid or a parallelogram, which has engendered the "slab" colloquialism. The slab-configured medium is disposed in an optical resonator having two orthogonal planes: (a) a "s" plane (transverse); and (b) a "p" plane (total internal reflection, TIR). Coherent light that is usually introduced to the laser medium about its longitudinal axis is totally internally reflected back and forth between the upper and lower surfaces of the parallelogram, exiting from the rear face of the slab. The slab laser medium internally self-compensates for thermal effects in the "p" plane. In the "s" plane, however, thermal effects can severely limit the laser performance. Optical effects are usually controlled by the selection of mirror and lens shapes, the adjustment of the mirror locations to varying focal points of the resonator, and the control of thermal effects and resonant conditions with respect to "p" and "s" planes.
The slab laser system of the present invention has achieved superior results heretofore unavailable with the prior art devices illustrated by the aforementioned patents.
The laser system of the current invention provides extremely high beam brightness, as well as reliability. The laser beam of 500 watts of average power is capable of drilling untapered holes and cutting straight edges in hardened alloys, such as Inconel and Hastalloy, to depths exceeding two inches. Beam quality is but a few times the theoretical diffraction limit. In contrast, the current rod shaped high-power Yttrium Aluminum Garnet (YAG) lasers can drill and cut the same materials only to a maximum depth of 0.75 inches.